How 700,000-Year-Old Rhino Bones Could Change the Story of Human Migration

A 700,000-year-old butchered rhino carcass in the Philippines is rewriting the history of early human migration around the globe, and telling us more about a tool-using human relative that lived long before Homo sapiens ever existed.

Researchers recently unearthed a rhino skeleton on Kalinga, a province within the Philippine island of Luzon. The skeleton showed signs of deliberate butchering by stone tools. But when these cuts were made more than 700,000 years ago, there shouldn't have been any tool-users around to butcher the animal—at least according to our old understanding.

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A study on the rhino skeleton was published today in the journal Nature. Here's what you need to know.

Who did this?

One thing is for sure—it wasn't Homo sapiens. The family tree of humans is bigger than just us, and includes our extinct close cousins like the Homo neanderthalis and Denisovan species. But there are more distant relatives as well.

The most likely candidate to have made these rhino cuts is Homo erectus, an ancient Asian species of human that went extinct around 140,000 years ago. The tools used on the carcass seem to corroborate this theory.

Nature

But the study authors concede there is a problem with this hypothesis. The Philippines are a fairly isolated chain of islands in the Pacific that, at the time, would have been accessible only by boat. According to the paper, "it still seems too farfetched to suggest" that any early human relative could have made the journey. And yet, the butchered rhino is there.

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How do we know something human did this?

Tools were recovered at the site that correspond to those known to have been used by early humans. In addition, marks on the rhino bones specifically correspond to abrasions one might expect a small human relative to leave behind.

In addition, there were no known large carnivores in the region at the time that could have made similar markings. Nor are the marks the byproducts of erosion. The cuts are too big to have been left by small carnivores, and they look a whole lot like carving by human tools.

"The natural marks present at the surface of the bones were observed and described and are clearly different from the ones we interpreted as cutting marks," says lead author Thomas Ingicco of the Muséum national d’Histoire naturelle in Paris.

There are also percussion marks on the skeleton that correspond to striking by humans, and nothing in the muddy natural environment that might have bruised the animal in such a way. The completeness of the skeleton, according to Ingicco, also suggests that the stone tools couldn't have coincidentally contaminated the site.

What do other scientists think?

Briana Pobiner, a Smithsonian research scientist who works on the diet of early humans, calls this an "exciting new discovery of well-dated stone artifacts associated with likely butchered extinct rhinoceros fossil bones" and other animals, far before Homo sapiens walked the Earth. It also seems to predate all known watercraft, and Pobiner says, "the evidence from Kalinga also adds to the growing indication that whether intentionally or not, at least one pre-modern human species of hominin was able to cross sea barriers in the Middle Pleistocene."

She adds that previous fossil evidence places early humans as having feasted on rhinos around 2 million years ago. (Note: Pobiner sent a follow-up email indicating that they likely scavenged, but did not hunt, rhinos as originally stated in this article.)

What's the main takeaway?

The movements of early human species have been a hot topic of debate, with Homo erectus having spread through the Asian continent earlier than other human species. As the earliest evidence for Homo sapiens is around 300,000 years ago, the rhino remains and stone tools predate the rise of our species by at least 400,000 years.

Despite comparatively smaller brains, the Homo erectus hunters, or perhaps another related species, had to cross the treacherous open ocean somehow to make it all the way to the Philippines—before the use of any known watercraft.

Mysteries surround these early tool-using primates, ancestors to the species of human that still exists today. We don't know exactly who they were, and we don't know exactly how they got there. However, the early human hunters of the Philippines apparently enjoyed the taste of rhino.

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